This invention relates to seats which include vibration compensating seat suspensions.
Seats of vehicles such as tractor-trailer trucks are subject to substantial vibration. Severe vibrations occur as vehicles travel rough road surfaces. A majority of seats now made for operators of such vehicles include vibration compensating suspensions beneath the seats. Such suspensions are in addition to the vehicle suspension systems which interpose the wheels of the vehicle and the vehicle bodies. A pervasive seat suspension is the parallelogram suspension. This suspension takes its name from a parallelogram linkage which is central to the suspension. The parallelogram suspension provides purely vertical movement of the seat during vibration.
A suspension much improved over the parallelogram suspension is the suspension of U.S. Pat. No. 3,711,149. The suspension of this patent is a "knee-pivoting" suspension. This suspension takes its name from a pivoting of the seat about the front of the seat during vibration. The pivoting is in the area of the knee of the seat occupant. Such pivoting is desirable because it minimizes movement of the lower leg during vibration. The knee of the seat occupant flexes as the seat pivots, maintaining foot contact with vehicle controls. While lower leg movement is minimized, the seat also improves the quality of the ride of the occupant by eliminating the tendency of the upper body of the occupant to strike the back of the seat during rebound from vibration (commonly called "back-slapping").